Tuesday, March 26, 2013

BMW i3 Pure Innovation?

File:BMW i3 Concept IAA.jpg

Something different. I like where BMW is going with their i3. Here is what I think about it:

The new compact BMW i3 model is a step forward for the company. The electric drive car will be available this Autumn. But it is not only BMW's first series produced electric car, it also introduces carbon-fibre-reinforced polymers in an industrial scale. The company risked a lot and here is why I think it will pay off.

China's coastal cities are suffering from the smog which is caused by both industry and automotive mobility. The crude oil price increased from under $ 30 per barrel in the Year 2000 to between $ 90 and $ 100 per barrel and the sluggish growth is one of the main factors keeping it from increasing further. We don't need any doomsday scenarios associated with peak oil to know that something has to change. California, with their zero emission vehicle program, and the EU, who want to enforce a emission target of 95 g(CO2) for the year 2020, also add an additional incentive for car companies to look for alternatives for gasoline and diesel.

BMW chose a different approach than GM - with their Cheverolet Volt - and Toyota. The car's primary engine is an electric drive with 170 HP output. A range extender (BMW calls it REx) with 54 HP can be ordered at a hefty price tag of 3000 €. This small gasoline engine, derived from one of BMWs own motorcycle engines, is connected to a generator to load the batteries. BMW claims fast charging the batteries to 80 % capacity can be achieved within 30 min, still a forced break that long after driving for only an hour is a major drawback. Only in the configuration with the REx is - in my opinion - flexible enough to actually pose a threat to traditional cars and other plug in hybrids. Without it, the range is said to be only 130 km to 180 km (80 mi to 100 mi) the REx almost doubles that.

One of the major disadvantages of all electric cars is that the batteries are very heavy. Even the modern lithium-ion battery pack of the Volt weighs in at close to 200 kg (435 lb). According to VW an additional 100 kg add 0.3 l/100 km to the fuel consumption. The same goes for electric cars. The low energy density of li-ion batteries makes this issue even more pressing. BMW therefore decided to just go all out in light weight construction. The passengers aren't surrounded by steel as in most other cars but by carbon fiber reinforced polymers. This structure sits on top of what BMW calls the drive module made from aluminium alloys, which houses the batteries, the engines and suspension. The car weighs "only" around 1300 kg (with REx) (under 2900 lb) compare that to a Volt(admittedly, the Volt is bigger) which is over 30 % heavier and you can see that BMW's approach was the right one.

File:London 01 2013 BMW i3 5688.JPG
Body of a BMW i3 (c) Mario Roberto Duran Ortiz

CFRP has some disadvantages compared to other materials. It is very expensive compared to steel or even aluminium. This is in large part due to the difficult industrial production. Most CFRP parts, one knows from racing or the aerospace industry, have to be hand built from carbon fiber sheets, which are placed in a mold and the applied polymer  then gives it the needed strength. BMW injects five layers of fiber directly with the polymer. It is then pressed (1800 t) and heat cured. Watch a video of the process. BMW plans together with their joint-venture partner SGL to reduce the cost of CFRP by 90 %.

The weight of a part compared to steel can according to AUDI be reduced by 50 % to 75 %. Since CFRP is very anisotropic, which means the material is stronger in fiber direction than across it, there is a higher cost for research and development associated.There are further issues which also have to addressed: recycling becomes more difficult and also even though crash behavior of CFRP is better than of steel, minor crashes might lead to major costs

So in conclusion: not only is the i3 going to be the first true electric drive car to be mass produced by a major company, it also has a very different, very innovative body-work. But it is still far from perfect. The low range and the very high cost for a small car of at least 40,000 € stop it from becoming a leap forward. The batteries remain the main problem. Electric drive alone also does not solve high CO2 production if the energy comes from old coal plants. Still for the company it will pay off. BMW is a few years ahead of every competitor in the use of CFRP and at least caught up to Toyota in electric mobility. So it will be seen as innovator for years to come.

No comments:

Post a Comment